Bobbin thread is balling up underneath and not allowing more than a couple of stitches before jamming.

try adjusting the needle thread right up to stop the bunching of thread that is causing the problem

if it' still under warrenty take it back and get another..if it's not under warrenty, try a new needle, make sure the top thread is not coming off the thread take up lever, make sure the bobbin is turned the right way in the bobbin case, also could be a timing problem

Thread balling up in the bobbin case usually indicates that the TOP thread is mis-threaded (usually at the take up lever). Check with your manual for proper threading path.

try changing the needle
rethread the machine top and bobbin
even try a different bobbin--make sure the bobbin is turned the right
way
make sure the top thread has not come off the thread take up lever

Make sure thread is not laying across the bobbin when you look down into the plastic slider that covers the top loading bobbin case. The bobbin on mine I observed was loose in the case so that as the machine ran, eventually the bobbin thread would jump out of the stitch finger (the silver piece to the far left of the bobbin case, past the tension slots). I solved this problem and so can you! Take the extra felt spool pin felt in your accessories kit that came with the machine, remove bobbin from case and drop this small felt circle into the bobbin case. Replace bobbin. On the 4423, the bobbin thread goes counter-clockwise and drops into the tension discs, and goes all the back until it falls into the space left of the silver stitch finger. Make sure take up level raised all the way up! Then pull the needle thread toward you until bobbin thread comes all the way up. If you start sewing and you actually can SEE the bobbin thread laying across the bobbin, STOP and tethered because that would mean your thread did not slide all the back behind the silver stitch finger--however, I assure you, if you go one step at a time, you did it correctly! You will be smiling in no time! Why? The felt helps to make the bobbin rest in the correct position to keep it from jumping out of the groove. I hope this helps you.
Jimmy

It very well could have a burr in on your bobbin case, If, it was me, I would take it to Sears sewing machine department and ask them what they think it could be. They sometimes have new bobbin cases right there for you to buy, depending how big your Sears is. It won't cost you anything, at least to find out from the saleman.

I would try adjusting the tension on the machine - this sometimes causes the bobbin thread to jam while sewing. Re thread the entire machine including the top thread. Also it is recommended to use new thread as old thread can ball up after time. If no luck I would call the store you purchased the machine from.

Hello,
Give these solutions a try.

* Un-thread your machine and remove your bobbin. Clean any loose thread or lint out of your
bobbin case. Re-thread your machine, reinsert and re-thread your bobbin.

* Change your bobbin as there could be a nick along the edge of your bobbin spool that’s catching your thread as you sew.

* When you start to sew a seam, Hold the upper and bobbin thread tails back and out of the way as you sew your first couple of stitches. This will keep them from getting jammed in your machine.

I hope this helps.

Hello,
Here are a couple of things to try.

* Un-thread your machine and remove your bobbin. Clean any loose thread or lint out of your
bobbin case. Re-thread your machine, reinsert and re-thread your bobbin.

* Change your bobbin
There could be a nick along the edge of your bobbin spool that’s catching your thread as you
sew.

* When you start to sew a seam, grasp the upper and bobbin thread tails. Hold them back
and out of the way as you sew your first couple of stitches. This will keep them from getting
caught in your machine.

I hope this helps.

Try moving the stitch length dial to 4 or 5 - check the manual. You may have it in the position for very close together sewing. I had to do a lot of trying with my 4795 to get it to work right. I found that very thin thread, polyester kind, broke at the needle after a couple of stitches. I switched to coats & clarks thread and a Singer ball point needle and it works fine. Be sure your needle is inserted with the flat top toward the back of the machine. Good luck!